[Vor. 8 
294 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
for completeness. Initial fluctuations in H-ion concentration 
generally occurred in the neutral and alkaline cultures. 
Mannite and Beet Decoction.—In a few experiments, a medium 
composed of a mixture of mannite and of beet decoction—the 
two in different proportions in different series— has been used. 
The method of preparation is a combination of those used with 
mannite and with beet decoction. First, a series with mannite 
and one with beet decoction were made. Then equal volumes 
of the mannite solutions of varying Py were placed in flasks 
and to each was added twice the volume of beet decoction with 
similar or closely agreeing Py. In the other series one volume 
of beet decoction was first added, and then twice the volume 
of mannite with the corresponding H-ion concentration. The 
resulting media were accordingly (1) 333 per cent mannite 
plus 66$ per cent beet decoction and (2) 66$ per cent 
mannite plus 333 per cent beet decoction. 
Hydrogen-ion concentration determinations of all colorless 
solutions were made at room temperature according to the usual 
colorimetric method of Clark and Lubs(’17). The solutions to be 
tested were, in all cases, allowed to stand at least 24 hours at room 
temperature in order to establish an equilibrium. Owing to 
the presence of color in the peptone and in the beet decoction 
solutions, it was necessary to use a colorimeter for the H-ion 
determinations. Two types of instruments, a Duboscq (micro) 
and a Kober have been used at various times in this work, the 
detailed method of which has been described by Duggar (’19). 
The H-ion values appearing in the charts, curves, and manu- 
script, unless otherwise specified, represent initial determinations 
and not final determinations. Certain changes in reaction during 
germination occur, but this phase of the topic will be considered 
subsequently in the diseussion. 
Solutions ranging in H-ion concentration from Py 1.2 to Pa 
9.2-10.04- were thus obtained with each medium. Experimental 
values were, in most cases, identical with the caleulated ones, 
and where the H-ion concentration was beyond the range of the 
extreme indicator, the reaction has been designated by adding 
““+” to the last value denoted by the indicator. With any 
medium the 12 or 13 solutions of varying H-ion concentrations 
